The BC96 monoclonal antibody reacts with human CD25, the 55kDa interleukin-2 receptor α chain (IL-2Rα). CD25 is expressed by early progenitors of T and B lineage as well as by activated mature T and B lymphocytes. By itself, CD25 binds IL-2 only with low affinity. However, CD25 associates with CD122 (IL-2 receptor β chain) and CD132 (common γ chain) to form the high affinity IL-2 receptor. CD25 plays a role in lymphocyte differentiating and activation/proliferation.